<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #box{
            width: 100px;
            height: 100px;
            background-color: #f00;
        }
    </style>
</head>

<body>
    <div id="box"></div>

    <script>
        let oBox = document.getElementById("box");
        oBox.onclick = function(){
            oBox.style.display = 'none';
        }

        document.onclick = function(){
            oBox.style.display = 'block';
        }
    </script>
</body>
</html>